1. Field of the Invention
The present invention relates to an optical-element holding mechanism and an image-shake correcting device adapted for use in an optical apparatus, such as an interchangeable lens for a single-lens reflex camera or the like.
2. Description of Related Art
To correct deterioration of lens performance resulting from manufacturing error, it has generally been practiced to arrange the lens-holding mechanisms of interchangeable lenses of single-lens reflex cameras to be suited for correcting optical axis deviations of lenses during a manufacturing process, i.e., for adjusting relative positions of a plurality of optical elements in a direction orthogonally intersecting an optical axis. The typical arrangement of the conventional lens-holding mechanism and a method generally employed for correction of the optical axis deviation are described below.
FIG. 1 shows the lens-holding mechanism which forms a part of a conventional interchangeable lens for a single-lens reflex camera. Referring to FIG. 1, a guide tube 1 is kept in a fixed position with respect to a film surface. A guide slot la is formed in the guide tube 1 to extend in the direction of an optical axis. A cam tube 2 is fitted on the outer side of the guide tube 1 in such a way as to be only rotatable around the optical axis. A cam slot 2a is formed in the cam tube 2.
A first lens tube 3 holds a first lens 5 and has its outer side fitted in the inner side of the guide tube 1. A roller 4 which engages the guide slot la and the cam slot 2a is attached to the first lens tube 3 with a screw. When the cam tube 2 is rotated around the optical axis, the roller 4 is moved accordingly at an intersection point of the guide slot la and the cam slot 2a to cause the first lens tube 3 to move in the direction of the optical axis.
A second lens tube 6 holds a second lens 7. The second lens tube 6 abuts on the rear end face of an arm part of the first lens tube 3 extending rearward in the direction of the optical axis and is secured to the arm part by a screw 9. The second lens tube 6 is thus arranged to move integrally with the first lens tube 3 when the first lens tube 3 moves in the direction of the optical axis.
In the lens-holding mechanism which is arranged in this manner, the relative positions of the first lens tube 3 and the second lens tube 6 are not exactly decided in the direction orthogonally intersecting the optical axis. In this direction, their positions are arranged to be roughly determined within a certain range. By virtue of this arrangement, optical axis deviations (eccentric deviations) of the first lens 5 and the second lens 7, due to manufacturing errors of parts, can be corrected by adjusting the position of the second lens tube 6 relative to the first lens tube 3 in the direction orthogonally intersecting the optical axis in assembling them.
The method for adjusting and correcting the optical axis deviation of the lens-holding mechanism during a manufacturing process is next described. In making the adjustment, the guide tube 1 is secured to an adjustment tool body (not shown) before the second lens tube 6 and the first lens tube 3 are fixed in position with the screw 9. Then, an adjustment tool 8 which is composed of an adjustment ring 8a, an urging ring 8b and an urging spring 8c is set. The adjustment ring 8a is fitted on the outer side of the lens holding part of the second lens tube 6. Then, the adjustment ring 8a is movable with respect to the adjustment tool body in the direction orthogonally intersecting the optical axis. The urging ring 8b is fitted in the inner side of the adjustment ring 8a and is urged toward the second lens tube 6 by the urging spring 8c which is disposed between the adjustment ring 8a and the urging ring 8b. 
Therefore, the second lens tube 6 is held in a state of being pressed against the first lens tube 3 by the urging ring 8b. In other words, the first lens tube 3 and the second lens tube 6 are kept in a state of being spaced at a fixed distance in the direction of the optical axis.
The above-stated optical axis deviation can be corrected by moving the adjustment ring 8a in the direction orthogonally intersecting the optical axis to bring the second lens tube 6 to a desired position in this direction. After the second lens tube 6 is moved, by using the adjustment tool 8, to the position where the optical axis deviations of the two lenses 5 and 7 are corrected, the screw 9 is tightened to couple the first lens tube 3 and the second lens tube 6 with each other in a state of having no optical axis deviation.
However, the conventional optical axis deviation correcting method has the following shortcomings.
Firstly, since the second lens tube 6 is arranged to be urged toward the first lens tube 3 by the urging ring 8b, the urging force is exerted on the first lens tube 3 or the abutting part of the cam slot 2a and the roller 4. Then, the optical axis deviation is corrected in a state of having the first lens tube 3 and the roller 4 deformed by the urging force. Therefore, the instant the urging force by the urging ring 8b is removed, the deformed parts tend to resume their original shapes to bring back the optical axis deviation. In this state, the optical axis deviation can be hardly considered to have been accurately corrected in actuality.
Secondly, the accuracy of correction deteriorates due to deformation of parts taking place when the screw 9 is tightened. For example, at the first lens tube 3, a part around the screw 9 is deformed by the tightening frictional force of the screw 9, particularly in a case where a self-tapping screw is employed as the screw 9. At the second lens tube 6 also, a part around the screw 9 is deformed by the frictional force of the head part of the screw 9. If the adjustment tool 8 is removed in the state of having such deformation, the second lens tube 6 tends to move in the direction of moderating a stress generated by the deformation. The optical axis deviation thus hardly can be considered to have been accurately corrected also in this respect.
Thirdly, a frictional force generated at the abutting faces of the first lens tube 3 and the second lens tube 6 while the position of the second lens tube 6 is in process of correcting adjustment also causes deformation of the first lens tube 3, which also deteriorates the accuracy of the correction.
Meanwhile, cameras are arranged nowadays to automatically perform all actions important for photo-taking, such as determining an exposure, focus adjustment, etc. Even a person who is unaccustomed to operating cameras, therefore, can take photographs with little possibility of failure.
Besides, factors of photographing failures have been almost completely eliminated by recent advancement of efforts to develop a system for correcting image shakes that often result from vibrations imparted to cameras.
Here, the system for correcting image shakes resulting from vibrations is briefly described. In taking photographs, the hands holding the camera generally vibrate within a frequency range from 1 Hz to 12 Hz. In order to take a photograph without any image shake despite such vibrations at the time of a shutter release, it is a basic concept to detect the vibration of the camera and then to vary the position of a correction lens according to the value of the vibration detected.
Therefore, in order to make it possible to take a photograph without image shakes under such condition, it is necessary to accurately detect the vibration of the camera and then to correct a change of the optical axis caused by the vibration of the camera by displacing a correction lens.
Theoretically, the vibration of the camera can be detected by means of a vibration detecting means for detecting acceleration, velocity, or the like and a displacement signal output means for outputting a displacement signal obtained by electrically or mechanically integrating a signal outputted from the vibration detecting means. The image shakes then can be corrected by displacing the correction lens on the basis of the displacement signal to vary a photo-taking optical axis as required.
An image-shake correcting system which uses such a vibration detecting means is next described in outline. FIG. 2 shows by way of example the arrangement of the image-shake correcting system. In the case of the system shown in FIG. 2, the system is arranged to suppress image shake of the camera taking place in the directions of arrow 81, including a vertical vibration 81p (direction of pitch) and a horizontal direction 81y (direction of yaw).
In FIG. 2, reference numeral 82 denotes a lens barrel. Vibration detecting means 83p and 83y are arranged to detect respectively the vibration in the directions of arrows 84p and 84y. A lens holding member 85 is arranged to hold a correction lens. Coils 87p and 87y are arranged to impart a thrust to the lens holding member 85. Detecting elements 86p and 86y are arranged to detect the position of the lens holding member 85. A position control loop is formed jointly by these parts. The stability of an image on an image plane 88 is secured with the lens holding member 85 driven according to the outputs of the vibration detecting means 83p and 83y which are used as target values.
Further, there have been developed image-shake correcting devices of varied kinds (as disclosed in, for example, Japanese Laid-Open Patent Application No. HEI 6-289465 which corresponds to U.S. Pat. No. 5,602,675).
The appearances of these image-shake correcting devices present cylindrical shapes as shown in Japanese Laid-Open Patent Application No. HEI 9-43661, etc. The body part of each of these devices includes a driving part for a lens and a part for driving a lock means to lock and unlock the movement of the lens.
However, the conventional image-shake correcting device is arranged to be secured to a fixed member within an optical apparatus and to be immovable in the direction of the optical axis in many cases. Such an arrangement has imposed some limitation on the optical design of the apparatus.
Further, in the case of an optical system having lens units disposed respectively before and after an image-shake correcting device arranged to be movable together, it is necessary to interlink the front and rear lens units with each other across the image-shake correcting device. However, if the conventional image-shake correcting device of the cylindrical external shape is used for such an optical system, the use of the image-shake correcting device necessitates a member used for interlinking the front and rear lens units to be disposed further outside of the outer side of the image-shake correcting device. Beside, a lens driving part and a lock-member driving part arranged in parallel with the optical axis prevent the optical apparatus from having recessed parts or hole parts provided by using dead spaces for preventing an increase in size. Therefore, the outside diameter of the optical apparatus inevitably becomes larger.
A first object of the invention is to provide an optical-element holding mechanism which can be simply arranged to be capable of accurately correcting deviation of an optical axis.
A second object of the invention is to provide an image-shake correcting device which is arranged to integrally interlink lens units disposed before and after the image-shake correcting device and to be movable in the direction of an optical axis without necessitating any increase in outside diameter thereof.
To attain the above objects, according to a first aspect of the invention, there is provided an optical-element holding mechanism, which comprises a first holding member arranged to hold a first optical element, a second holding member arranged to hold a second optical element, a coupling member, such as a screw, arranged to couple the first and second holding members with each other and to permit relative positions of the first and second holding members to be varied in process of being coupled, and an urging member disposed between the coupling member and the second holding member and arranged to urge and press the second holding member against the first holding member at least when the coupling member is in process of coupling the first and second holding members.
The optical-element holding mechanism is preferably arranged to prevent deterioration of accuracy of correction of an optical axis deviation resulting from deformation of the first holding member by mounting a deformation restricting member arranged to restrict the deformation of the first holding member taking place in varying the relative positions of the first and second holding members and also when the coupling member is in the process of coupling the first and second holding members.
It is also preferable to prevent deterioration of accuracy of correction of an optical axis deviation resulting from deformation of the second holding member by arranging a friction preventing member between the coupling member and the second holding member to prevent generation of a frictional force by the coupling action of the coupling member between the coupling member and the second holding member. Further, the friction preventing member is preferably arranged to have its movement restricted, with respect to the first holding member, within a plane of varying the relative positions of the first and second holding members and also to be movable together with the first and second holding members after completion of assembly work.
The friction preventing member may be arranged to serve also as the deformation restricting member, and the urging member may be disposed between the coupling member and the friction preventing member. Deformation of parts thus can be efficiently prevented by simple arrangement.
Further, to attain the above objects, according to a second aspect of the invention, there is provided an image-shake correcting device mounted on an optical apparatus and arranged to move a lens relative to a body member in a direction orthogonally intersecting an optical axis, the image-shake correcting device having a recessed part formed in a peripheral part of the body member to allow a component member of the optical apparatus extending before and after the body member in a direction of the optical axis, such as a member arranged to interlink optical elements disposed before and after the image-shake correcting device, to be located inside of the recessed part.
More specifically, the image-shake correcting device comprises a body member, lens driving means mounted on the body member and arranged to drive a lens, a lock member arranged to lock and unlock the movement of the lens by moving relative to the body member, and lock driving means for driving the lock member, wherein a recessed part is formed in a part of a peripheral part of the body member, other than parts where the lens driving means and the lock driving means are mounted on the body member.
Further, the image-shake correcting device and, therefore, the whole optical apparatus, can be compactly arranged, for example, by arranging a restricting part in a dead space available on the inner side of the recessed part, to restrict the movement of the lens in the direction of the optical axis and also by arranging the lens driving means and the lock driving means approximately within one and the same plane orthogonally intersecting the optical axis.
These and other objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.